#### Answer

400 by 800 rectangle

#### Work Step by Step

We know that the memorial must be at least 200 feet away from the boundary of the park. Thus, we find the dimensions of the park:
$$ 1200-(2)200=800 \\ AND \\ 800-(2)(200) =400$$
The locus of points is a 400 by 800 rectangle in the center of the rectangular park.